The tank known from EP 0 870 877 B1 is joined from the outer side by clamp-shaped quick connectors from two identical cup-shaped plastic material injection moulded parts having opening edge structures which fit on each other. A sealing is inserted between the opening edge structures. The tank e.g. can be used without a separation wall as a rain water tank. This tank is known under the trade name “Herkules”, according to leaflet K26, edition 2006 “Kleinklaranlagen und Fäkalien-Sammelgruben” (Minor Sewage Plant and Cesspool/Septic Tank Collection) of the company Otto Graf GmbH, Kunststofferzeugnisse, D-79331 Teningen, pages 22, 23, and may also be used for collection basins. In this case and provided that several chambers are needed, several of these tanks are installed and are connected via piping for communication.
The leaflet K26, starting on page 4 also discloses minor sewage plants “System Aqua-Simplex” which are based on a cylindrical tank having round end caps. The tank is installed lying horizontally and is monolithically produced by rotation moulding. A separation wall is integrated by rotation moulding in the middle part of the tank. The tank can be used as a single tank sewage plant for treating water in two chambers. The separation wall either separates the chambers totally or allows a communication via an elevated spillover. The leaflet also describes embodiments of the rotation moulded tank in which the separation wall integrated by the rotation moulding process seals at the edge in watertight fashion but has a central throughhole. These embodiments can be used as collection basins or anaerobic digesters. The rotation moulding process is expensive and not very rational, requires large tools and machines, costly material and long cycle times. The separation wall formed by the rotation moulding process is situated in a fixed position. To transport that rotation moulded tank may cause significant transport problems and high transport costs, in particular in the case of a large tank volume. Manipulating the tank in most cases needs the use of a hoisting gear.
In tanks known from U.S. Pat. Nos. 4,325,823 A and 6,280,614 B which are joined from at least two differently shaped parts separation walls are installed which substantially fill the inner cross-section of the tank and which are anchored at their edges. Manufacturing and mounting each separation wall which is produced with the full or almost full cross-section of the tank is complicated, in particular in the case that a portion of the separation wall mounted in one tank part protrudes into the other tank part.